In the general type of core-manufacturing method that we are concerned with, magnetic strip material is wrapped in superposed relationship about the window of the core to build up a core form, and the core form is later annealed at elevated temperature to relieve stresses therein. A problem that arises in such manufacture is that the pressure of the wrapping and other pre-annealing operations and the heat of the annealing operation often produce, within the core, regions where juxtaposed layers of strip material adhere together and form relatively low resistance paths, or shorts, between the adhering strip layers. Such internal adhesions or shorts are undesirable because they can produce within the core, transversely of the flux path therethrough, low resistance closed circuits for eddy currents; and such closed circuits have the detrimental effect of reducing the effective net cross-section of the core, the amount of such reduction being a direct function of the cross-sectional area bounded by such closed circuit or circuits.
Application Ser. No. 07/726,239--Lee et al, filed Jul. 5, 1991, issued as U.S. Pat. No. 5,134,771, assigned to the assignee of the present invention, and incorporated by reference herein, discloses several different methods for reducing the number of such internal shorts that are present in the final core. These methods all involve breaking up the internal shorts after they have formed during annealing.